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THE RÔLE OF PROGESTERONE IN THE MECHANISM OF PELVIC RELAXATION IN THE MOUSE
Author(s) -
Hall Kathleen
Publication year - 1949
Publication title -
quarterly journal of experimental physiology and cognate medical sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0033-5541
DOI - 10.1113/expphysiol.1949.sp000942
Subject(s) - relaxin , endocrinology , medicine , pregnancy , relaxation (psychology) , mechanism of action , uterus , action (physics) , chemistry , receptor , biology , biochemistry , physics , genetics , quantum mechanics , in vitro
1. Experiments were carried out on 234 oöphorectomised mice with the aim of discovering whether progesterone plays an active rôle, such as that described for the guinea‐pig, in the mechanism of pelvic relaxation in the mouse. 2. When 1·0 or 1·5 mg. progesterone was injected daily for 8‐19 days into œstrogenised mice, the interpubic gap as measured on X‐ray photographs was 0 to 0·6 mm., i. e. no wider than would be produced by œstrone alone, and not comparable with the considerable separation which follows relaxin administration or occurs in normal pregnancy. 3. When 1·0 mg. progesterone was injected daily into œstrogenised mice, the effect on symphyseal separation of concurrent or subsequent administration of relaxin was largely prevented. 4. When progesterone and œstrone were injected concurrently into mice whose pelves had been rendered sensitive to œstrogen, the action of œstrone was much impaired. 5. The results of the experiments provide no evidence that progesterone itself is effective in producing symphyseal separation in the mouse, or can augment the action of œstrogen on the symphysis, or can act indirectly by causing the production of endogenous relaxin. 6. It is suggested that in pubic separation produced by œstrogen and relaxin the action of œstrogen is fundamental, and that the inhibitory effect of progesterone on the separation is caused by antagonism between progesterone and œstrogen. 7. The possibility is discussed that the pelvic changes which take place during the latter part of pregnancy in the mouse depend upon the presence of a low progesterone/œstrogen ratio in the body at this time, and that a species difference may exist in this respect between the mouse and the guinea‐pig. The expenses of this work were defrayed by a grant from the Research Committee of the University of Birmingham. I should like to thank Professor S. Zuckerman for X‐ray facilities in the University Department of Anatomy, and Dr. R. G. Britt and Mr. L. Glazebrook for preparing the X‐ray photographs. I am indebted also to Dr. F. S. H. Marshall, of British Schering Ltd., for a generous gift of progesterone.